Scientists have discovered 17 million year old sperm in some rocks in Australia, sperm that belonged to ancient shrimp and was about as long as the body of the crustaceans themselves.

"The Riversleigh fossil deposits in remote northwestern Queensland have been the site of the discovery of many extraordinary prehistoric Australian animals, such as giant, toothed platypuses and flesh-eating kangaroos," said Professor Mike Archer of the UNSW School of Biological, Earth and Environmental Sciences in a release. "So we have become used to delightfully unexpected surprises in what turns up there." He also noted that it's very exciting to find fossilized sperm (seen balled up in the image above) with the sperm nuclei intact, especially given that they're soft tissues.

Archer told the Washington Post that they found some of the sperm inside a fossilized female shrimp. "The sperm was clearly wound up in knots within this weird 'zenker' organ, balled up like a ball of string, then literally shot at and into a female and the female catches it. It's like they were playing catch," he said.

How did the sperm keep for so long? That part of the story involves bat shit:

The steady rain of poo from thousands of bats in the cave would have led to high levels of phosphorous in the water, which could have aided mineralisation of the soft tissues.

These are not the only creatures who have developed giant sperm but they are certainly the most impressive this week.